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Is Hydrogen The Jet Fuel Of The Future?

Hydrogen, the most abundant element in the universe, has been touted as a superior alternative to lithium-ion batteries in cars, but adoption has been painfully slow. For all the hype, one would think most cars would be running on hydrogen already, yet they are not. So where are hydrogen proponents going wrong?

According to some, they may be focusing on the wrong sort of vehicles to power with hydrogen. True, there are billions of passenger cars on the roads around the world. But there are also millions of aircraft in the skies – or there used to be. The aviation sector may well be the game-changer for hydrogen.

One executive from this nascent hydrogen segment explains it in terms of energy intensity and utilization. Valery Miftakhov from ZeroAvia, developers of zero-emission powertrains for aircraft powered by hydrogen, says aircraft have much higher energy intensity and utilization than cars. As such, they should be the focus of attention for hydrogen backers.

In anarticle for Aeronautics Online, Miftakhov compared intensity and utilization rates for cars and aircraft, in other words the portion of the vehicle’s weight dedicated to fuel and the amount of time it spends in motion. Cars, he said, have an energy intensity average of some 2 percent and energy utilization rates of about 5 percent. A Boeing 737, on the other hand, has an energy intensity average of close to 40 percent and a capacity utilization average of 40 percent, spending about 10 hours daily in the air.

What does this all mean, and why does it matter?

It means that planes are much greater energy guzzlers than cars, which is not news. It also means that it is a much better target for hydrogen fuel cell technology developers than passenger cars, for which, Miftakhov says, “even the current batteries are good enough.” There is simply not enough demand for a lot more energy-dense energy sources in passenger cars.

Yet in air transport, things look different, especially now, amid the coronavirus pandemic. The pandemic grounded millions of flights, which greatly reduced CO2 emissions. Now there are calls for a green recovery from the pandemic, and hydrogen-powered aircraft may find their place in this green recovery.

In comparison, a California company, HyPoint, makes hydrogen-fueled powertrains that sportenergy density of 530 Wh per kg. It is now working on another version of the powertrain that would have energy density of up to 960 Wh per kg. According to ZeroAvia’s Miftakhov, hydrogen fuel cell systems could reach an energy density of up to 3,000 Wh per kg.

What’s so important about energy density? Things like length of journey, to mention the most basic. The more energy a battery - or fuel - cell can store, the longer it can remain in motion without needing to recharge.

Higher energy density, in other words, extends the range of a vehicle.

But there’s more. There is also the matter of emissions. The air transport industry generates some 115 grams of carbon dioxide per passenger-kilometer, which adds up to 859 million tons of emissions annually, notes Berkant Göksel, an engineering entrepreneur and co-founder of Electrofluidsystems. Göksel and his colleagues at Electrofluidsystems justreleased a set of drones and air taxis, all hydrogen-powered, using plasma technology and capable of traveling at superhigh speeds. Because, according to them, this is the future: fast and emission-free.

“Governments of developed countries have new strategies for green gas and hydrogen which can be produced with zero CO2 emissions. This is most important in a sustainable energy supply,” Göksel told Oilprice.com. “We can imagine air taxis with amazing ranges up to 1000 km and beyond, which would also personalize regional air mobility.”

Of course, for all this promise in the air transport industry, hydrogen is not without faults, and challenges remain. Some expertsnote hydrogen fuel cells’ poor specific power output and the fact that range is not necessarily the top priority in air transport.

There is no universal solution for all priorities in the transport industry. Yet Zeroavia’s Miftakhov certainly has a good point: the success of a product depends on its target market. Hydrogen technology developers may well have been wrong in focusing mostly on passenger cars. Its characteristics appear to be much better suited for longer-haul, more energy-intensive journeys than the daily commute to work. There is definitely a lot going on in hydrogen powertrains for aircraft. Maybe it will lead to wider adoption of hydrogen fuel cells, given the right encouragement from governments and other decision-makers. Air transport could become a game-changer for hydrogen.

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Fascinating article raising the issue that different applications require different energy density or intensity. I first encountered this idea in Barry Commoner's book Poverty or Power: Energy and the Economic Crisis (1976). Commoner had argued that there is a fundamental mistake of considering energy efficiency only through the lens of the First Law of Thermodynamics of conservation of energy. It is not just the % of the amount of energy turned into power to accomplish a task that is important but also the appropriate density of energy to match the density required for the task.

Commoner had argued that it was wasteful to ignore efficiency according to the Second Law of the Thermodynamics that states energy for ever degrades from greater concentration to a more diffuse state. It states that as energy is transferred or transformed, its quality is wasted as it loses density. Efficiency according to the Second Law of Thermodynamics then is achieving a task with the minimum energy density required. It is silly according to Commoner to use nuclear energy, which is better suited for smelting metals that need 1500ºC to heat a room that requires 20ºC.

If hydrogen is denser energy than electric batteries, lithium or otherwise, it may be more appropriate, according to the 2nd Law of thermodynamics it is better suited for air transportation that requires higher quality, more concentrated energy.

peep rada on May 18 2020 said:

Until there is no clean source of hydrogen, there will be no future for hydrogen.
Clean means also efficiency. If only 20% of energy can be forwarded from clean energy sources, that low efficiency is a clear waste of expensive materials and workforce.

Ronald Wagner on May 20 2020 said:

Natural gas has been used to fly airplanes. It is extremely abundant and is available in almost all areas. It is far cheaper than hydrogen, and can be used as Liquified Natural Gas for high density. Liquefication can be done at the airport. Certain design modifications can be made, if needed, for extended flights.

The push for hydrogen is mainly motivated to make higher profits for the renewables industry and make them more competitive with natural gas. Neither hydrogen, solar, or wind are truly competitive over the complete life cycle. Natural gas is virtually a free energy source. It is as natural gas wind or the sun's rays.

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